Video: Brain function during coma

Terry Wallace suddenly woke up last year — 19 years after an auto accident left him unable to communicate or move on his own. His recovery, though limited, is still extraordinary.

One-quarter of a million Americans have severe brain injury and most are not expected to recover. But what goes on in their brains while they're out of touch with the world?

The results from Dr. Joy Hirsch's lab at Columbia University Medical Center offer some important and fascinating clues. Hirsch was surprised by how much the brains of unconscious people actually function.

"When I first saw these results I was shocked because we expected that the response functions would be more or less flat," says Hirsch.

In fact, brain scans show that in two patients the areas of the brain that control language lit up when they heard recordings made by family members.

"We were not able to distinguish them from normal patients when we asked them to listen to narratives of their family members speaking to them," says Hirsch.

The scientists emphasize that both Wallace and the patients in this latest study, while severely injured, were in what is called a "minimally conscious state."

"Most of these patients follow commands," says Dr. Nicholas Schiff of Weill Medical College at Cornell University, who worked on the study. "They can move to commands. Some of them even make attempts to communicate, can mouth a word. Maybe occasionally, on a rare occasion, [they] establish communication."

By contrast, Terry Schiavo — the focus of an intense court battle over life support in Florida — is in what doctors call a "persistent vegetative state," less responsive with almost no chance of recovery.

Still, the latest results indicate the possibility that many brain-injured people have more activity in their minds than anyone previously knew.